Matlab ROS subscriber basic example

Have you a step by step example to create a subscriber I do this

setenv('ROS_IP','192.168.1.41') % adress PC with Matlab setenv('ROS_HOSTNAME','192.168.1.41') setenv('ROS_MASTER_URI','http://192.168.1.28:11311/') % adress turtlebot rosinit rostopic list

Here I am able to see all the topics that are on the turtlebot And I am able to command to move my turtlebot with

velocity = -0.1; % meters per second robot = rospublisher('/mobile_base/commands/velocity') velmsg = rosmessage(robot) velmsg.Linear.X = velocity; for i=1:50000 i send(robot,velmsg); end

I can also ask to my Turtle to emitting a noise

soundpub = rospublisher('/mobile_base/commands/sound', 'kobuki_msgs/Sound') soundmsg = rosmessage('kobuki_msgs/Sound'); soundmsg.Value = 6; % Any number 0-6 send(soundpub,soundmsg);

But when I want to subscribe to a topic…

odom = rossubscriber('/odom')

odomdata = receive(odom,3);

I have this error message

Error using robotics.ros.Subscriber/receive (line 325)

The function did not receive any data and timed out.

When I apply : rostopic info /odom I obtain :

Type: nav_msgs/Odometry Publishers: * /mobile_base_nodelet_manager (<http://turtlebot.local:58513/>) Subscribers: * /matlab_global_node_86572 (<http://192.168.1.65:49791/>) * /matlab_turtlebot_69671 (<http://192.168.1.65:49752/>)

What I should do to be able to subscribe and read a topic of my Turtlebot with Matlab My configuration is Turtlebot : Ubuntu 14.4 + Indigo PC : Windows10 + Matlab 2017a (I stop all firewall)

Thank you in advance for your help

Answer 1

[Vincent Talon]

My problem come to multipl IP adress for my Matlab computer...

.

To help other persone, the configuration that work well with my Turtlebot

In my case, the IP adress are

PC with Matlab : 192.168.1.41

Turtlebot computer : 192.168.1.28

.

In the .bashrc, I have

source /opt/ros/indigo/setup.bash

export ROS_MASTER_URI=http//192.168.1.28:11311

export ROS_HOSTNAME=192.168.1.28

export ROS_IP=192.168.1.28

.

In Matlab 2 solutions are possible:

solution 1:

setenv('ROS_IP','192.168.1.41') % adress PC with Matlab

setenv('ROS_HOSTNAME','192.168.1.41')

setenv('ROS_MASTER_URI','http://192.168.1.28:11311/') % adress turtlebot

rosinit

.

solution 2 :

rosinit('http://192.168.1.28:11311', 'NodeHost', '192.168.1.41')

[xupeng]

thanks for your answer， it soluts my problem whice disturbe me for a long time .

Answer 2

[Sebastian Castro]

If you try to echo the /odom topic on the Turtlebot and in MATLAB (same syntax), do you see any messages?

rostopic echo /odom

If you don't see anything on the robot, then it's not sending anything and it's not a MATLAB issue. If you see something on the robot but not in MATLAB, then it could be a connectivity issue and maybe changing the port on the URI could help?

- Sebastian